No hot water, and the little window at the bottom of your gas water heater is dark. The pilot light is out. Sometimes relighting it is all it takes; sometimes it won't light, or it lights and goes right back out.
This is for gas tank water heaters with a standing pilot. Many newer heaters light electronically instead, and Rinnai's tankless heaters, for example, use direct-spark electronic ignition with no pilot at all. If yours is tankless and showing a code, see Rinnai error codes.
First: do you smell gas?
If you smell gas (a rotten-egg smell), don't try to light anything. Southwest Gas says to leave the area immediately, avoid anything that could make a spark, and call 911 and Southwest Gas at 877-860-6020 from a safe distance.
Relight it the way the label says
Every gas water heater has lighting instructions on a label on the heater itself. Follow those exactly; the steps and the knob positions differ between brands and models. If there's no label or you're not comfortable doing it, stop there and call.
If it won't light or won't stay lit
These are the common causes InspectAPedia lists for a pilot that won't stay lit:
- The thermocouple. It's the small sensor in the pilot flame that tells the gas valve the pilot is lit. If it's out of the flame, loose, damaged or worn out, the valve shuts the gas off and the pilot goes out, often the moment you let go of the knob. A defective thermocouple usually just gets replaced.
- A dirty or clogged pilot. Dirt or debris in the pilot assembly or its small gas opening makes a weak flame that won't keep the thermocouple hot.
- Gas supply. A closed valve, low gas pressure, or an empty propane tank means a weak flame or none.
- Drafts and air. A draft can blow the pilot out, and a heater that doesn't get enough combustion air can't burn properly. That second one is also a carbon monoxide concern.
- Water dripping onto the pilot. A leak from the heater that drips on the pilot can put it out, and it means the tank needs a look anyway.
- The gas control valve. Less common, and a job for a trained gas technician.
What's DIY and what isn't
Relighting by the label is something many homeowners do. Replacing a thermocouple is a common repair, but it's gas work: if you're not sure, have a pro do it. Anything with the gas valve, gas pressure, venting or a gas smell is technician work.
If your heater keeps having problems and it's past 10 years old, it may be time to look at replacement. See signs your water heater needs replacing.
OX Plumbing repairs and replaces water heaters across the East Valley, gas and electric, and we answer 24/7. Our $99 service call covers the visit, the diagnosis and an upfront price before any work begins.